I had always thought that God wasn't delaying for us to get our act together, but that He does have a 'fixed' number of total souls in His mind throughout all of His creation, and the 'delay' is actually His plan to give every soul it's incarnated 'turn at bat' so to speak, afterwhich he will return. He does know each of us from before the foundations of the world, and he knows the end from the beginning.
God's soverignty over man's free will is not in question. Just like a parent who has sovereignty over their children and a plan for their children, the parent still encourages their children to exercise and mature their free will, and intervenes only when the parent thinks best (for reasons a child will never fathom and unaware of the myriad ways until they mature).
The argument I thought you'd offer (which I think is stronger though still unsatisfying) is that 2 Pet3:9a alludes to God being patient toward 'us' [the brethren, the object of his epistle] and thus 2 Pet 3:9b further refers to 'any of us' and 'all of us'.
But I think there is a better reconciliation of God's sovereignty in election/reprobation and His designing 'free will' into His creation, without us having to insert words into His scripture (any of His scripture)....but I don't yet know what it is.